Phosphate flotation



United States Patent Int. Cl. B03d N06 US. Cl. 2093 Claims ABSTRACT OFTHE DISCLOSURE A method of beneficiating phosphate rock by anionic frothflotation by scrubbing a deslimed phosphate rock feed with an alkalinecomposition, dewatering and desliming the scrubbed feed, conditioningthe thus treated feed with an anionic flotation reagent and subjectingthe conditioned feed to a froth flotation of high grade phosphateconcentrate.

This invention relates to the beneficiation of phosphate rock andsimilar phosphatic materials and in particular to an improved method oftreating phosphate rock flotation feed to obtain a high grade phosphateconcentrate.

In the usual process for beneficiating such phosphatecontaining material(hereinafter referred to collectively as phosphate rock), the mixture ofphosphatic minerals and gangue obtained from the phosphate deposit ormine is first washed to remove trash therefrom and to separate andrecover the larger lumps of phosphate minerals (usually referred to aspebble rock). The remaining material (washer reject material) consistsof a mixture of phosphate rock particles, sand, clay and similar ganguematerials, substantially all of which is less than about 10 mesh (TylerStandard), and preferably is less than 14 mesh in size. The phosphaterock consituent of this material is then concentrated and recovered forsubsequent use, commonly by froth or table flotation techniques or acombination of both. Patents No. 3,013,664 and 3,086,654 toHollingsworth and Sapp disclose efficient and economical methods ofbeneficiation utilizing froth flotation operations comprising cationic(silica) floats and anionic (phosphate) floats. At present, mostflotation processes use a anionic float followed by a cationic float.

In such anionic floation operations the phosphate rock feed is commonlyfirst deslimed and dewatered, conditioned with an anionic flotationreagent, and subjected to a froth flotation operation, all as describedin the Hollingsworth and Sapp patents noted above. In conventionalpractice the phosphate rock feed is sometimes scrubbed, as a slurry withwater, prior to desliming and dewatering to aid in removal of adherentmaterials.

While superior to previous methods, the anionic flotation operation isnot entirely satisfactory in that large quantities of anionic flotationreagents are consumed adding to the cost of beneficiation. Equallyimportant, the flotation is not selective enough, resulting in asignificant proportion of insolubles (mostly silica) being separatedalong with the phosphate.

A method has now been found whereby the amount of anionic flotationreagents required for effective flotation isgreatly reduced, while atthe same time the selectively of the float is increased.

Briefly stated, the present invention comprises the method ofbeneficiating phosphate rock by froth flotation comprising scrubbing aphosphate rock feed with an alkaline "ice composition, conditioning thescrubbed rock feed with an anionic flotation reagent consistingessentially of a fatty acid and a fuel oil, and subjecting theconditioned feed to a froth flotation operation to float a finalphosphate concentrate which is recovered as thedesired phosphateproduct. In its preferred embodiment, the process also comprisesdewatering and desliming the scrubbed phosphate rock feed prior toconditioning.

As to materials, the alkaline composition is preferably an aqueoussolution of caustic soda. Other alkaline materials that may be used aresoda ash, lime, ammonia, potassium hydroxide, magnesium hydroxide, andthe like alkaline materials capable of raising the pH of an aqueoussolution to at least about 8 and preferably about 9 and above. It iscommercially uneconomical to use a pH above 11 because of the amount ofalkaline material required.

As to the proportions, the alkaline material is present in the scrubbingfluid in amount suflicient to adjust the pH of the fluid to about 9 andpreferably 10. When caustic soda (NaOH) is the alkaline material to beadded to the feed scrubbing step (scrubbing ordinarily is carried out at65 solids) it is used in the proportion of from about 0.005 part toabout 0.05 part by weight for each parts weight of phosphate rock feed.

The anionic flotation reagent is a combination of a fatty acid and afuel oil. No alkaline materials are required as part of the reagent asis the case with anionic flotation reagent combination used heretoforein flotation of Florida phosphate rock feeds. The fatty acid may beoleic acid, linoleic acid, tall oils, rosin, mixtures thereof, and otherlike materials commonly used in anionic flotation reagents In likemanner, the fuel oil can be any commonly employed in anionic flotationreagents such as diesel oil, kerosene, Bunker C fuel oil, and mixturesthereof. The reagent is preferably a combination of 4 parts by weight ofa fuel oil to each part by weight of a fatty acid, although proportionsranging from 1:1 to 8:1 can be used.

As to equipment the dewaterer, deslimer, conditioner, and flotationapparatus can be those disclosed in the Hollingsworth and Sapp patentsdiscussed above or those commonly used in phosphate beneficiation. Thescrubber is preferably a standard attrition type scrubber.

As to processing conditions, a phosphate rock feed is first passed intoa scrubber where it is scrubbed with the alkaline composition for timesuflicient to render the sur face of the phosphate rock suflicientlyalkaline; ordinarily about 20 to about 60 seconds are required for smallscale operations and up to about 3 minutes in large commercialinstallation. Longer treatment times can be used, but, again, this isnot commercially desirable. The treatment time will vary, dependent uponthe type of scrubbing equipment, the type and concentration of alkalinematerial in the scrubbing liquid. The optimum conditions are readilydeterminable by making test runs and noting the conditions showing theleast amount or reagent used and the greatest recovery of phosphate.Phosphate recovery is measured as percent by by weight of bone phosphateof lime (tricalcium phosphate) recovered or percent B.P.L. recovered.Using an amount of caustic soda in the scrubber solution to give a pH ofabout 10, it is found that treatment of phosphate rock' feed for about60 seconds will result in greatest percent B.P.L. recovery and lowestreagent consumption. If the feed has not been first subjected to acationic flotation is should be deslimed prior to scrubbing.

3 After scrubbing, it is preferred to deslime and dewater the phosphaterock feed to remove slime produced in the scrubbing operation. Slime,either phosphatic or clay, if present in any appreciable amount, act tolower the effectiveness of the anionic flotation.

to eliminate variatons due to equipment differences. The amount ofalkaline material used in scrubbing and amount of anionic reagent usedare measured in pounds per long ton of phosphate rock feed.

Example 1 The phosphate rock feed 1s then conditloned by being Therecess of th resent inventio was m r d admixed with an anionic flotationreagent of the present p e p H CO Pa 6 .nventio The exam 168 Set forthbelow Show that the with conventlonal procedures using a 29.72% B.P.L. i1 f th H flota phosphate rock feed. The feed was scrubbed in a seriesmven Ion reqmres 68$ 0 a i h of runs, with and without caustic soda, forvarious periods non reagefts B (fatty an fue P t an of time at 65%solids using a turbo-type mixer. The that requlre? li More Pamculajfly w30 1 several scrubbed feeds were then deslimed and condi- 40% 16553111011113 1101311011 reagent 1 an Increase 111 tioned with varyingamounts of anionic flotation reagents selectivity (less insolubles)wh1le mamtaimng the same or containing 4 parts by weight of fuel oil to1 part by weight better B.P.L. recovery. of fatty acid and floated in astandard flotation cell. The The invention will be further described inconnection fuel oil used was Bunker C fuel oil API gravity 19-20 withthe following examples of the practice of it WhlCh and the fatty acldwas Unitol OT (a tall oil fraction). are set forth for purposes ofillustration only. The results are summarized in Table 1.

TABLE 1 Serubbin Lbs., Reag Concentrate Middling Tailing ent 11F. Lbs.,Feed Percent NaOH/ Wt. Wt. Wt. B.P.L. 4:1 Run No. Time 'I.F. B.P.L.Insol. percent B.P.L. Insol. percent B.P.L. percent B.P.L. Reey. MixNaOH Standard Phosphate Floats {Caustic added to conditioner) 1 secondsNone 29. 72 61. 71 3. 7 03 None 29. 72 01. 71 20.5 70.75 2.17 7.0 00.5872.5 13.07 07.0 3.7 .00 None 29.72 01. 71 20.0 77.19 2.70 7.2 00.92 72.813.18 07.1 3.7 .10 None 29. 72 01. 71 19.0 70.41 2. 39 0. 5 04. 12 74. 515. 19 01.1 3. 7 11 None 29. 72 01. 71 3. 7 .43 None 29. 72 01. 71 34. 474. 74 4. 50 3. 4 30. 94 02. 2 4. 80 89. 5 5. 0 10 None 29.72 01. 7119.9 75.73 2.86 10.9 04.04 09.2 11.58 72.0 5.0 .43 None 29. 72 01. 7130. 5 72. 73 0. 17 5. 5 19. 07 58. 0 3. 45 92. 7 8. 1

Efieets of Scrubbing With Caustic (No caustic used in conditioner) 9 15seconds--- .40 29.72 01. 71 12.4 70.52 2.00 9.5 70.73 78.1 17.20 54.13.7 None 10 30 seconds .22 29.72 61.71 6.1 65. 49 15.89 93.9 26.17 19.93.8 None 11.. 0 .43 29.75 01. 71 33.0 74.90 3.10 3.0 38.20 02.8 5.2388.5 3.7 None 12 do- .43 29.72 01. 71 29.7 70.00 2.01 4.9 53.40 05.47.24 83.6 3.7 None 13-- do .43 29.72 01. 71 20.9 70.18 2.08 8.0 00.1071.1 11.92 71.0 3.7 None 14-. do .05 29.72 01.71 33.0 75.40 2.87 3.4 48.93 03.0 4.58 90.0 3.7 None 15 .-do .05 29.72 01. 71 37.0 73.84 5.71 3.220.73 59.8 3.08 92.4 5.0 None NH4OH 10 do .43 29.72 01. 71 20.0 70.18 2.0.0 60.81 68.0 8.40 80.4 3.7 None 1 These conditions produced no float.1 N o float. a Feed was not deslimed after scrubbing.

In the following examples, beneficiation runs were made Example 2 withthree different phosphate rock feeds in order to take into considerationvariations in flotation characteristics which exist from one feed toanother. All the scrubbing, desliming, dewatering, conditioning, andflotation of the A 30.89% B.P.L. phosphate rock feed was used andvarious treatments, with and without scrubbing and including variationsin time, were used. The conditioning and flotation procedures used werethe same as that used feeds was carried out on the same equipment forall runs in Example 1. The results are summarized in Table 2.

TABLE 2 Concentrate Middling Tailing Lbs. Reagent] Scrubber T.F.

Per- Per- Per- Percent N aOH/ Feed, cent cent cent B. 4:1 Run No. TimeT.F. pH B.P.L. Wt. B.P.L. Insol. Wt. B.P.L. Wt B.P.L. Ratio Reey. MixNaOH pH Standard Phosphate Floats (control) Effects of Scrubbing 19 30seconds- None 1 7. 5 30.89 21. 5 72.48 8. 83 78. 5 20.00 4. 82 48. 7 5.4 4 9. 2

20 do 7 30.89 34. 4 76. 57 3. 69 .23 62. 7 5. 2. 83 87. 6 5. 8 None 21d0 6 1O 2 30.89 32. 5 77.61 2. 37 4. 2 45.08 63. 3 6. 34 2. 90 86. 6 5.4 None 9. 0

30 vs. 60 sec. Scrubbing 22 30 seconds. 7 10. 4 30. 89 37. 0 75.48 5. 062. 6 22.06 60.4 3. 2. 66 91. 9 5. 4 None 9.0

23 60 seconds 7 10. 3 30. 89 36. 0 75.87 4. 56 2.8 26. 66 61. 2 4. 45 2.70 91.0 6. 4 None 9.0

1 pH of ores in the mixer prior to adding flotation reagents.

5 Example 3 The process of the present invention was compared toconventional anionic floats employing no scrubbing and conventionalanionic floats utilizing scrubbing. The other processing conditions usedwere the same as that used in Example 1. The results are summarized inTable 3.

6 3. The method according to claim 2 in which the alkaline material isused in an amount sufficient to adjust the pH of the solution to atleast about 8.

4. The method according to claim 1 in which the phosphate rock feed isscrubbed with the alkaline composition for about 20 second to about 3minutes.

TABLE 3 Concentrate Middling Tailing Lbs. Reagent/T.F. Percent NaOH/Feed, Percent Percent 6 Percent B.P.L. 4: 1 Run No T.F. pH B.P.L. Wt.B.P.L. Insol. Wt. B. P'L. Wt. B.P.L. Ratio Reey. Mix NaOH pH StandardPhosphate Floats 36. 66 9. 7 80. 55 1. 46 15. 7 74. 18 74. 6 22. 17 4.03 54. 5 5. 4 3 9. 5 36. 66 37. 6 79. 05 3. 68 3. 8 37542 58. 6 9. 52 2.56 84. 2 7. 6 3 9. 36. 66 37. 6 78. 38 4. 33 4. 4 35. 42 '58. 0 9. 85 2.55 83. 8 8. 8 3 9. 0 36. 66 39. 78. 28 4. 55 4. 5 29. 67 56. 0 8. 64 2.49 85. 8 8. 8 3 9. 2

30 Sec. Scrubbing Without daustic 36. 66 25. 3 79. 67 2. 02 8. 9 64. 5565. 8 15. 14 2. 99 72. 6 5. 4 3 36. 66 39. 2 76. 71 5. 58 3. 2 19. 8657. 6 10. 75 2. 55 82. 1 6. 6 3 9. 2 36. 66 41. 5 77. 70 4. 63 4. 1 26.23 54. 4 8. 78 2. 47 85. 8 8. 8 3 9. 2

Sec. Scrubbing With Caustic; v

31 3 10 36. 66 41. 5 77. 43 4. 66 3. 5 95 55. 0 6. 58 2. 36 89. 6 6. 2None 9. 2 32 3 10 36. 66 40. 7 78. 46 3. 56 3. 5 32. 04 55. 8 6. 26 2.37 90. 3 5. 8 None 9. 2

While the exact theory is not precisely understood, it is believed thatscrubbing of the phosphate ore in the presence of an alkaline materialprior to conditioning acts to clean the surface of the ore and to makethe surface more alkaline or positive. This more positive charge on theclean surface, in turn, renders the separation in the anionic float moredefinite, greatly reducing the amount of insolubles separated with thephosphate and requiring much less anionic flotation reagent foretfective flotation.

The anionic floation procedure of the present invention can bused aloneto beneficiate washer reject material or in conjunction with cationicfloats carried out prior to or subsequent to the anionic flotation.

The scrubbing with alkaline material is also beneficial for cationic(silica) flotation as it acts to reduce the amount of reagent necessarywhile maintaining the same or better B.P.L. recovery.

What is claimed is:

1. The method of beneficiating phosphate rock by froth flotationcomprising scrubbing a deslimed phosphate rock feed with an alkalinecomposition, dewatering and desliming the scrubbed feed to remove slimeformed during scrubbing, conditioning the phosphate rock feed with ananionic flotation reagent consisting essentially of a fatty acid and afuel oil, and subjecting the conditioned feed to a froth flotationoperation to float a final phosphate concentrate which is recovered asthe desired phosphate product.

2. The method according to claim 1 in which the alkaline composition iscaustic soda.

References Cited UNITED STATES PATENTS 2,313,360 3/1943 Ralston 209-1662,336,437 12/ 1943 Erickson 209-166 2,424,552 7/ 1947 Clemmer 209-1662,660,303 11/1953 Maseman 2O95 3,302,785 2/1967 Greene 2095 3,349,90310/1967 Olsen 209-166 X OTHER REFERENCES Taggart, handbook of MineralDressing, Wiley and Sons, Inc., New York, 1945, 3-15, 3-17, 10-01,10-07, TN 500 T3, 1945.

HARRY B. THORNTON, Primary Examiner.

R. HALPER, Assistant Examiner.

US. Cl. X.R. 209-12, 166

